Cardiac transplantation has become a widely accepted surgical treatment in patients with end-stage cardiomyopathy. Recent advances in surgical technique and post-operative management have yielded increasing survival rates. Little is known, however, about the immediate or long-term effects of this procedure on the brain, particularly its influence on the cerebral circulation. The overall objective of this study is to determine the time course of cerebral blood flow (CBF) changes before and after cardiac transplantation, and to relate such changes to cardio- hemodynamic variables and to neurological and neuropsychological function. Approximately 120 patients will be studied over a 3-year period, half of whom are in severe cardiac failure prior to heart transplant. Regional cerebral blood flow measurements will be made noninvasively by the Xenon-133 intravenous method at four specific time points: (1) pre- transplantation, (2) between 18 and 36 hours post-transplant, (3) between 3 and 5 weeks post-transplant (pre-discharge), and (4) at 6 months follow-up. The CBF measurements, including calculated cerebrovascular resistance, will be related to concurrently measured cardio- hemodynamic variables; specifically, cardiac output, cardiac index, systemic perfusion pressure, and systemic vascular resistance. Both the CBF and cardiac variables will, in turn, be correlated with the results of neurological an neuropsychological examinations obtained at the same time. The hypothesis is made that reduced cardiac output in the failing heart will adversely affect cerebral blood flow, and that this will be correlated with disturbances in neurobehavioral function, especially manifested by cognitive deficits. In addition to the expected global reductions in CBF, particular attention will be paid to regional CBF abnormalities (delineated by 32 detectors), and their possible relation to focal neurological and neuropsychological impairment. It is anticipated that cardiac transplantation will at least partially ameliorate cerebral circulatory disturbances and normalize neurobehavioral function. A principal aim of the study is to determine the extent to which this occurs. In a special subproject, cerebral blood flow will be evaluated in patients with a temporary artificial heart (Jarvik-7), and compared with the findings following subsequent transplantation.